If you’re a frequent patron of the movie theater, you have probably noticed the trend. Almost three-quarters of the films are based off of something else, and the hottest new source is young adult (or YA) fiction.

Now, I say new source, but YA books have been hitting the silver screen for decades.

If you count children’s stories and middle-grade books, they have been around even longer. But let’s trace it back to where the modern boom started: Harry Potter and the Sorcerer’s Stone.

Harry Potter was a teen/tween smash, so it is no surprised that the movie adaptation was a hit among the target demographic. The movie invited new fans, hooking adults and other audiences to the story.

The trend started catching on with adaptations of Twilight, the vampire romance the internet loves to hate, The Princess Diaries, which only some are aware are actually books, and The Hunger Games, the novel-to-film that made dystopia cool again.

Harry Potter spawned eight films from seven books, earning over $7.7 billion and clocking in at the most lucrative movie franchise of all time. (It also started the trend of splitting one book into multiple parts with Harry Potter and the Deathly Hallows Part 1 and Part 2, but that’s a topic for another article.)

As popular as Harry Potter was, most critics agree that it was The Hunger Games that acted as a catalyst for the YA adaptation deluge.

Not only did The Hunger Games create lifelong fans of the book and movie series, generate $408 million dollars, and become the first film since Avatar that stayed #1 for four consecutive weekends, it skyrocketed Jennifer Lawrence to the status of America’s Darling and the rest of the cast and major crew members into the spotlight.

All of a sudden, producers, directors, and actors alike wanted in. The Fault in Our Stars, If I Stay, The Giver, Divergent, and The Maze Runner are just a few of the films that followed in The Hunger Games’ footsteps, hoping to land in the same place as their competitors.

This year alone, there will be thirty-six movies based on books, almost half of which are based on Young Adult novels.

There are multiple reasons YA books are so easy to make into movies. First off, the script is almost written for you. The plot is there, dialogue is there, and the action is already plotted out.

Don’t get me wrong, it still takes effort to adapt fiction into a screenplay, but working from an established concept certainly helps.

Speaking of established, another thing adaptations have going for them is the fanbase that will surely accompany the movies.

Even movies that are generally considered bastardizations of the source material (such as Percy Jackson and the Olympians: The Lightning Thief and Eragon) opened strong, with Percy Jackson even releasing another film in 2012.

With every successful film, more and more fans are added, and it is widely accepted that most fans will go see a movie even if it’s received a plethora of bad reviews – you know, out of principle.

Beyond even that, YA books usually come in series and more recently trilogies. The Hunger Games will have four films, and if they follow the current trend each one will gross more than the last. Like The Hobbit, there is potential for one book to be converted into multiple movies.

In general, the last book of the series will be adapted into two or more films (such as Mockingjay Part 1 /2, Breaking Dawn Part 1 /2, Harry Potter and the Deathly Hallows Part 1 /2), generating even more money and allowing them to stick to the source material better to ensure a good audience rating.

YA has staked its claim on the big screen as a strong seller and a way to push lesser-known actors and actresses into the spotlight. It’s established, it’s popular, and it’s making more money than ever. Even if people start to notice that YA is taking over as the #1 source for book adaptations, this train is not slowing down, and I doubt that it’s planning on stopping any time soon.